Cardiovascular responses to external compression of human calf muscle vary during graded metaboreflex stimulation

This study investigated the cardiovascular response to a standard external muscle compression during concomitant muscle metaboreflex stimulation of varying intensity in human calf muscle. Eleven healthy male subjects (mean (s.d.) age, 26 (5.6) years; height, 177 (5) cm; weight, 74.3 (6.8) kg) were seated in an isometric dynamometer with the angle of the knee at 90 deg, and the angle of the ankle at 85 deg. After a 150-s rest period, subjects were asked to either perform isometric plantar flexion at 20, 30, 40, 50, 60, 70 or 80% of previously determined maximum isometric contractile force (MVC) for 90 s, or to sit at rest for this period. A thigh cuff maintained circulatory occlusion throughout the exercise period and for 180 s post exercise. After 60 s of post-exercise circulatory occlusion (PECO), a calf cuff was inflated to 300 mmHg for 60 s followed by a further 60 s of PECO alone after which the thigh cuff was deflated. During PECO the mean arterial pressure (MAP) increase from rest was dependent upon the preceding exercise intensity (P < 0.001). Compression elicited a further significant change in MAP, and the magnitude of this change from the PECO baseline was also dependent upon the preceding exercise intensity (P < 0.01). These results are compatible with activation of a metabolically sensitised population of mechanoreceptive afferents in human muscle during external compression.